Molds used in the production of lacquered polyurethane-molded articles, such as those used to mold lacquered polyurethane foam articles, have heretofore been pre-treated with a thin layer of an external mold release agent applied directly to the mold surface before a layer of a lacquer coating is applied to the mold. These steps have been followed by the injection into the mold of a desired polyurethane-based plastic. After the polyurethane-based plastic cures sufficiently within the mold, the mold is opened and the molded article is removed, or "de-molded." Such external mold release agents have provided for the complete release of the lacquer coating from the surface of the mold allowing the lacquer coating to be removed from the mold intact with the molded article. Examples of external mold release agents known in the prior art include tetrafluoroethylene, waxes dissolved in solvents, and silicon compounds.
However, the use of external mold release agents has been shown to have one or both of the following disadvantages. It is known that a thin coating of external mold release agent is invariably present on the surface of the lacquer coating after de-molding. This thin coating of external mold release agent can be present in sufficient amounts to prevent adhesion of a second coat of lacquer upon the first lacquer coat unless the mold release agent residue is removed by time-consuming and costly procedures. Providing such a second coat of lacquer to the molded article is often commercially desirable for either an improved exterior gloss, or to provide additional colors for detailing, decoration, printing or designs. Secondly, it is also known that thin layers of external mold release agent may remain on the mold surface after each production cycle, which over many production cycles builds to the point of requiring removal, resulting in undesirable production interruption.
It is also known to incorporate mold release agents or mold release catalysts directly into the in-mold lacquer coatings used in the production of polyurethane-molded articles. These internal mold release agents and catalysts of the prior art assertedly provide a mold release function within the lacquer coating itself, doing away with the need for external mold release agents, while also providing for re-coatability of the lacquer coating without the necessity of cleaning residues from the surface of the initial lacquer coating.
However, heretofore it has not been known to incorporate silicon-based mold release agents directly into lacquer coatings for use in the production of polyurethane-molded articles without first reacting such silicon-based compounds with other constituents to render the silicon compounds suitable for use as mold release agents. In U.S. Pat. No. 4,478,893, issued to Schonfelder et al., for example, there is disclosed polyisocyanate addition products useful as mold release agents in the production of molded lacquer coated plastics by the in-mold coating process. This reference discloses the use of polysiloxanes that have isocyanate reactive end groups and that are difunctional in isocyanate addition reactions as starting materials that must be further reacted with an excess of polyisocyanate and an alcohol, or amine, to produce the internal mold release agent disclosed in Schonfelder et al. Indeed, in Example 35 (comparative example) of Schonfelder et al., it is taught that a technically simple and nonspecialty polydimethylsiloxane compound, that is one without isocyanate reactive end groups and one that has not been further reacted in the manner taught in Schonfelder et al., is not suitable as a mold release agent for in-mold lacquer coatings.
The lacquer coatings of the present invention include an effective amount of a polydimethylsiloxane fluid that functions as an internal mold release agent to provide a complete mold release function, but which is present in an ineffective amount to prevent the adhesion of a second coating of the same or similar lacquer coating after de-molding. The lacquer coatings of the present invention therefore provide for the effective use of a silicon compound as an internal mold release agent of the type the prior art teaches is not suitable as a mold release agent for use in in-mold lacquer coatings.